The present invention relates to reaction resin mixtures of organic polyisocyanates, organic polyepoxides and certain accelerators (catalysts) wherein the mixtures are curable by the action of heat to form plastics containing isocyanurate groups and oxazolidino groups. This invention also relates to the use of such resins for the production of composites of all kinds and for the production of coatings and bonding agents of the most varied kind. The reaction resins according to the invention are furthermore suitable for use in mold making.
Reaction resin mixtures of organic polyisocyanates, organic polyepoxides and certain catalysts, prepared by polyaddition of polyepoxides and polyisocyanates with the use of catalysts, are known. In this connection the catalysts used are, in particular, tertiary amines (see for example, DE 3,600,764, DE 3,807,660, DE 3,644,382 and DE 3,904,156). The use of the known reaction resin mixtures, especially in mold making and tool manufacture, however, encounters difficulties in practice. This is due to the speed of curing of the mixtures using the known accelerators and accelerator systems, which are also referred to, for example, in DE 3,807,660 or DE 3,904,156. These known accelerators or accelerator systems cause either too rapid or too slow a curing of the mixtures. Accordingly, it is not easy to avoid shrinkage, cracking and bubble formation in the reactions which proceed rapidly. On the other hand, it is desirable for economic reasons, that the conversion reaction proceedS within a commercially reasonable time.
Therefore, the object of the present invention is to provide heat-curable reaction resin mixtures which cure in economically reasonable periods without excessive evolution of heat and which avoid shrinkage, crack formation, and bubble formation when they are used to produce or manufacture tools and molds.
It has surprisingly been found that using a mixture of specific tertiary amines as reaction accelerators avoids the previous problems while heat-curing in a reasonable time.